A number of devices can make use of small “micro” lenses, including lenses having a diameter and/or largest dimension less than about 5 mm, preferably less than about 1 mm, and more preferably about 800 micrometers or less. Although embodiments of the present invention can be used in connection with many different devices or applications, micro lenses are believed especially useful in connection with certain optical storage and/or read/write devices such as compact disks (CDs) and/or digital versatile disks (DVDs) and read or write apparatus used in connection with CDs or DVDs. Small lenses are especially useful in connection with small form-factor and/or low weight devices including those described in U.S. patent applications Ser. Nos. 09/315,398; 09/652,975; and 09/457,104, incorporated herein by reference.
Despite the fact that (as described below) the small size of such lenses may present opportunities for reducing the cost and/or increasing the quality of lenses, many approaches to fabricating small lenses have used technology substantially similar to those used in connection with relatively larger lenses. Accordingly, it would be useful to provide small lenses, and system methods and apparatus for manufacture, which can exploit at least some of the opportunities which are available as a result of the small size of micro lenses.
At least some lens making approaches have failed to provide relatively large numbers of lenses per process step and, indeed, many previous approaches provide only a single lens at a time, (i.e., such that a process step is applied to only a single lens or lens blank and/or apparatus such as a molding or grinding device is applied to only a single lens or a lens blank at any one time). Accordingly, it would be useful to provide a system, method and apparatus which makes it economical and feasible to provide high quality micro lenses which are formed many-at-once, such as forming or processing at least about 1000 lenses at once, preferably at least about 3000 lenses at once.
One of the disadvantageous aspects of some older lens fabrication approaches is the relatively slow cycle time, which is exacerbated when lenses are fabricated, e.g., one at a time. For example, some previous lens fabrication approaches involve a molding process. A typical cycle time for glass lens molding is around 60 to 90 seconds (or more) per cycle. When lenses are formed (in any given molding apparatus) one-at-a-time, this, of course means that a process time of 60 to 90 seconds or more is required per lens even when a continuous or “production line” process is used. Accordingly, it would be useful to provide a system, method and apparatus for fabricating micro lenses which can achieve a per-lens (effective) cycle time substantially less than about 60 seconds.
Another potential disadvantage associated with molding of glass lenses is that molding typically uses relatively low-temperature glass. Accordingly, some lens molding approaches are restricted in the lens materials that can be used. These material restrictions can, accordingly, place limitations on performance parameters such as index of refraction, dispersion and/or can affect lens cost. Accordingly, it would be useful to provide a system, method and apparatus which can achieve effective and economic micro lens production without being restricted to low temperature glass.
In at least some lens mnolding approaches, molding is achieved by compressing heated glass between the two opposed, typically concave, end surfaces of movable “pins”. Such approaches can lead to variances (with respect to nominal shapes or dimensions), e.g. in the lens thickness and/or alignment of lens surfaces owing to such factors as lateral or angular misalignment of pins or axial mis-positioning (e.g., as the pins are moved towards one another) and/or end surface wear, scratching and the like. Accordingly, it would be useful to provide a system, method and apparatus which can avoid at least some of the lens thickness variability or other variabilities in the fabrication of micro lenses.
In many previous approaches, following fabrication, lenses were coupled to separate devices such as mounting rings and the like. This typically involves providing additional gluing (or other coupling) steps, contributing to overall fabrication costs. Accordingly, it would be useful to provide a system, method and apparatus which can provide desired functions, such as providing mounting surfaces, optical or other stops and the like, while reducing the number of components and/or the steps or procedures for gluing or otherwise coupling components.
Another advantageous feature of etched lenses is a consequence of the fact that if photolithography is already used to define the shape of the lens, this process may be modified to allow inclusion of features such as diffractive surfaces or sub-wavelength features. Diffractive surfaces facilitate the use of a wider range of materials, since chromatic aberrations may be at least partially eliminated using a diffractive surface.